1. Field of the Invention
The invention relates to mats upon which golfers may execute practice shots simulating conventional play, and more particularly to golf mats directed to duplicating the feel of a golf shot on natural turf.
2. Description of the Related Art
The path of a club head during a properly executed golf swing has several components. As it is travelling toward the ball in a downward arc it has both forward-horizontal and downward-vertical moments. At the low point of its arc its motion is purely horizontal. And, of course, beyond that its motion is both horizontal and upward.
Two critical elements are in the path of a club head following this arc, the golf ball and the turf below it. In the great majority of shots, the club head makes contact with the turf as well as the ball. During some of these, the club head contacts the turf and ball simultaneously; other times the turf is contacted first. This all depends upon where the low point of the swing's arc resides.
When using an iron and purposely taking a "divot" the turf is struck after the ball, the low point of the arc in that case being beyond the ball's position and below the turf's surface. After striking the ball the club head is rapidly but smoothly decelerated as it digs into the turf. Then, for some time after reaching the low point of its arc, the club head travels upward through the turf as it scoops out and accelerates the divot. This practice of "hitting down on the ball" and taking a divot is useful in that it gives the ball backspin, enabling the golfer to better control the ball's flight as well as its roll after hitting the ground.
When executing a swing upon a practice mat it is desirable that the mat provide a realistic, natural-turf feel with respect to all the aforementioned components of the swing's arc. This is especially true when practicing divot-taking shots. That is, cushioning should be provided for the downward-vertical moment, resistance against the horizontal moment should be present, and the feel of taking and accelerating a divot in an upward, forward direction should be simulated.
Numerous devices have been developed to simulate the feel of a natural turf execution of a practice golf swing. The simplest type of golf practice mat is a stationary one, having an upper surface of artificial grass such as Astro Turf. Such stationary mats do not simulate an actual fairway shot because they fail to provide the combination of cushioning, resistance and yielding one feels when golfing on natural turf.
Attempts have been made to simulate the actual feel of fairway, divot-taking shots by utilizing practice mats which are moveable in the direction of golf ball travel. These moveable mats also show a reduced susceptibility to wear in the areas where the club head frequently contacts the mat's surface. One such device is that shown in U.S. Pat. No. 3,712,628 issued to Boss in 1973. Boss discloses a continuous belt of artificial turf from which a golf ball may be driven. However, Boss fails to include means for providing realistic resistance against the horizontal component of a swing, the belt and rollers of his device being designed instead to minimize resistance against the club head. Further, the number of moving parts Boss uses would seem to make his device fairly expensive and more prone to failure. It is also apparent that the Boss device could not accommodate those seeking to practice alternative shots, such as those requiring a "golf tee."
Another such device is shown in U.S. Pat. No. 4,311,312 issued to O'Brien in 1982. That device comprises a pad of artificial grass which is slidably mounted within a rectilinear frame, and has resilient means connecting the front and rear ends of the pad to the frame. The frame is positioned adjacent a stance pad. In O'Brien's 1982 patent the artificial grass rests on and slides directly on a rigid, stationary base mat. Thus, while O'Brien claims that this structure results in a realistic feel of taking a divot on a fairway, it would seem that the club head would be brought to an abrupt and unnatural stop after it inevitably hits the rigid base underlying the artificial turf. That is, adequate cushioning of the vertical component of the swing does not seem to be provided. Further, said mat would tend to collect sand and dirt within its closed frame, thereby inhibiting its reciprocating action. Finally, the 1982 O'Brien device employs a sliding pad having an exposed turf edge at its trailing end upon which the head of a golf club may easily catch thereby seriously interrupting a golfer's swing.
U.S. Pat. No. 4,387,896 resulted from a continuation-in-part of O'Brien's 1982 patent and was issued in 1983. This latter patent shows a variation of the device claimed in its parent patent; herein the slidable pad of artificial grass slides on a slippery surface. Side rails and end rails border the slidable pad, said rails having recesses shaped to receive the pad's outwardly-projecting tongues, these restricting its motion to the horizontal plane. The tongues form the backing or base of the artificial grass pad. No resilient means are used in this device; its structure is said to permit the entire slidable mat to move forward in a horizontal plane when the golf club hits the ball.
This structure would be subject to the same inability to clear itself of dirt, and likelihood of catching club heads on its trailing edge, as the device of O'Brien's 1982 patent. Further, its horizontally-projecting tongues as received by the rails, recesses serve to restrict the pad strictly to horizontal movement. This fails to accommodate the upward vertical component of a swing as it normally exists when a divot is being lifted out of the surrounding turf. That is, O'Brien's tongues prevent any lifting up of the slidable pad because their length is bound under the side rails.
Finally, O'Brien's failure to provide resilient means in the device of his 1983 patent requires that the pad be repositioned after each swing and ignores the value of said means in finely tuning the feel of the mat's resistance against a swinging club head.
Lindquist, in U.S Pat. No. 4,130,283 issued in 1978, discloses a golf practice device including a planar, U-shaped stationary section with a sled which is moveable within the U and held in the retracted position by a spring or other resilient means. The entire device is overlain with artificial turf which is cushioned by a layer of foam rubber. In both the stationary and moveable parts of the device, the foam rubber is mounted inside a frame which, in turn, is mounted on a rigid base. The sled has "Teflon" rails on its underside which slide on mating rails of the same material on the base. The sled also has tongues along its entire length on each side, the tongues engaging mating grooves or slots in the adjacent stationary frame.
Lindquist's device is impractical in view of its complexity and probable expense of constructing its frame. Further, being rigid, its frame would be subject to breakage, making the mat's entire structure vulnerable. In addition, uniform support is not provided beneath the artificial turf surface of his mat; cushion underlies some areas, others are supported by frame members, and still others have no support at all. Most notably, the projecting tongues along the sled's entire length, and the mating grooves along the entire length of the U's interior, prevent the sled's upward movement and interfere with the action necessary to approximate the feel of taking a divot. And, the trailing edge of Lindquist's sled is so constructed as to permit golf clubs to catch on it and tear the artificial turf layer loose.
Even though mats with moveable pads are particularly suited for practicing shots with irons, one may also desire to practice drives with woods from said same mats. Although the feel of cushioned turf is not as crucial in that case, the desirable sensation of yielding and the advantage of reduced wear to the mat's surface may nevertheless be realized. To facilitate driving practice, inclusion of means for accommodating a golf tee is necessary. However, Lindquist's device is the only one of the aforementioned mats including such means. Lindquist provides a vertically-extending opening in the upper foam surface of his mat for this purpose. However, this opening would seem prone to rapid wear and likely to clog with broken tee stems.
In my earlier U.S. Pat. No. 4,596,392 issued in 1986, I disclose a clayey deposit for supporting a golf tee, although this is in the context of a stationary mat. Further, said deposit remains exposed during use and therefore tends to be fairly rapidly depleted.
In sum, none of the foregoing devices provides a durable, simply-constructed, wear-resistant practice golf mat able to simulate the feel of a shot, especially a divot-taking shot, from natural turf.